Tall buildings: design, construction and operation | 2012 Issue IV

Inside Canada’s “Marilyn” Towers

Creating an Energy-Producing Skyscraper

Fluid-based Aerodynamic Performance

Ice, Snow and Tall Buildings

Assessing Korea’s Technology Potential

Talking Tall with Bjarke Ingels

In Numbers: Canada Rising

Reports: Shanghai Congress & 2012 Awards

CTBUH JournalInternational Journal on Tall Buildings and Urban Habitat

Council on Tall Buildings and Urban Habitat

S.R. Crown HallIllinois Institute of Technology 3360 South State StreetChicago, IL 60616

Phone: +1 (312) 567 3487Fax: +1 (312) 567 3820Email: info@ctbuh.orghttp://www.ctbuh.org

About the Council

ISSN: 1946 - 1186

The Council on Tall Buildings and Urban Habitat, based at the Illinois Institute of Technology in Chicago, is an international not-for-profi t organization supported by architecture, engineering, planning, development and construction professionals. Founded in 1969, the Council’s mission is to disseminate multi-disciplinary information on tall buildings and sustainable urban environments, to maximize the international interaction of professionals involved in creating the built environment, and to make the latest knowledge available to professionals in a useful form.

The CTBUH disseminates its fi ndings, and facilitates business exchange, through: the publication of books, monographs, proceedings and reports; the organization of world congresses, international, regional and specialty conferences and workshops; the maintaining of an extensive website and tall building databases of built, under construction and proposed buildings; the distribution of a monthly international tall building e-newsletter; the maintaining of an international resource center; the bestowing of annual awards for design and construction excellence and individual lifetime achievement; the management of special task forces/working groups; the hosting of technical forums; and the publication of the CTBUH Journal, a professional journal containing refereed papers written by researchers, scholars and practicing professionals.

The Council is the arbiter of the criteria upon which tall building height is measured, and thus the title of "The World’s Tallest Building" determined. CTBUH is the world’s leading body dedicated to the fi eld of tall buildings and urban habitat and the recognized international source for information in these fi elds.

2 | This Issue CTBUH Journal | 2012 Issue IV

advanced technologies are already having a dramatic impact.

After the Congress, CTBUH organized several tours for delegates in Beijing, Changsha, Hong Kong, Nanjing and Shenzhen. This gave delegates fi rst-hand insight into growing cities in China. We at CTBUH take pride in playing such a central role in giving our members and colleagues access to the latest ideas and knowledge about emerging design trends and technologies. But there is always more to do. The Council can play a larger role in many areas aff ecting the industry, such as sharing up-to-date information on building codes in cities around the world and the latest data on industry innovations. To accomplish these goals, the Council needs to continue to grow and it requires more active participation from members.

In addition to providing global forums like the Congress, CTBUH also recognizes individuals and teams who have made remarkable achievements in the design of tall buildings. This year at the 11th Annual Awards Symposium, Ceremony & Dinner in October we saluted three individuals. For his simple and elegant designs, Helmut Jahn received the Lynn S. Beedle Lifetime Achievement Award, and the Fazlur R. Kahn Lifetime Achievement Medal went to Charlie Thornton and Richard Tomasetti, structural engineers who helped design many of the most innovative and advanced tall buildings around the world. The recognition of Charlie and Richard is the fi rst time the CTBUH panel has awarded the prize to two people. My congratulations to Helmut, Charlie and Richard and to the recipients of “Best Tall Building” design awards. They are an inspiration to everyone in our industry.

All the best,

Dennis Poon, CTBUH Trustee / Thornton Tomasetti

When I fl y from Shanghai to New York, it usually takes me a few days to bounce back from the time change and 16 hours in the air.

But this time, when I returned from the CTBUH 9th World Congress Shanghai, I was so energized by the meeting that I wanted to stop everyone and tell them about it.

My thanks to the more than 850 delegates (a sold-out Congress!), sponsors and speakers for three days of valuable presentations, stimulating panel discussions, and networking events. For anyone who did not get a chance to attend, the three days are summarized on the CTBUH website.

This was our fi rst CTBUH Congress in China, which will soon set a record for the most tall and megatall buildings – buildings taller than 600 meters – in the world. The speed of urbanization in China and globally is unprecedented in human history: never before have so many people migrated to cities so quickly. China now has 15 cities with an estimated population of more than fi ve million. Building up is the most economic, sustainable and practical way to address this rapidly changing demographic.

My one line summary of the Congress is to quote the science fi ction writer William Gibson: “The future is already here – it’s just not evenly distributed.” When you walk around Shanghai – and other thriving cities across Asia – you have a sense that you are walking into the future of what a modern city can become. Embodying the Congress theme of “Asia Ascending: Age of Sustainable Skyscraper City,” many notable presentations indicated that present and upcoming designs incorporate the principles of sustainability at every level. In addition, many projects are paying more attention to the integration of new structures within the local context – the goal is not to be simply iconic but to also humanize the designs. I also noticed that Building Information Modeling and parametric modeling are being widely utilized, providing further evidence that

This Issue

EditorKevin Brass, CTBUHkbrass@ctbuh.org

Associate EditorsRobert Lau, Roosevelt Universityrlau@ctbuh.org

Antony Wood, CTBUH/Illinois Institute of Technologyawood@ctbuh.org

Editorial BoardAhmad Abdelrazaq, Samsung CorporationMir Ali, University of Illinois at Urbana-ChampaignRichard W. Bukowski, Rolf Jensen & Associates, Inc.Mahjoub Elnimeiri, Illinois Institute of TechnologyGary C. Hart, Weidlinger AssociatesPeter Irwin, RWDITim Johnson, NBBJZak Kostura, ArupGary Lawrence, AECOMSimon Lay, AECOMSam Lee, Guangzhou Scientifi c CommitteeTony McLaughlin, Buro HappoldPhilip Oldfi eld, University of NottinghamLester Partridge, AECOMJason Pomeroy, Pomeroy StudioSwinal Samant, University of NottinghamSteve Watts, AECOM Davis LangdonPeter Weismantle, Adrian Smith + Gordon GillMichael Willford, Arup

Design & LayoutTansri Mulianitmuliani@ctbuh.org

Steven Henryshenry@ctbuh.org

Published byThe Council on Tall Buildings and Urban Habitat© CTBUH 2012ISSN: 1946-1186

Council on Tall Buildings and Urban HabitatS.R. Crown Hall, Illinois Institute of Technology3360 South State Street, Chicago, IL 60616

t: +1 312 567 3487f: +1 312 567 3820e: info@ctbuh.org www.ctbuh.org

Copyright © 2012 Council on Tall Buildings and Urban Habitat. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, without permission in writing from the publisher.

Image CopyrightCTBUH Journal has endeavored to determine the copy-right holders of all images. Those uncredited have been sourced from listed authors or from within CTBUH

Print This Journal is printed by Source4, Chicago.

Front cover: Absolute World Towers © Tom ArbanBack Cover: Absolute World Tower 56 © Tom Arban

Supporting Contributors are those who contribute $10,000; Patrons: $6,000; Donors: $3,000; Contributors: $1,500; Participants: $750.

(As of October 31, 2012)

CTBUH Organizational Members http://membership.ctbuh.org

SUPPORTING CONTRIBUTORSAECOMAl Hamra Real Estate CompanyBroad Sustainable Building Co., Ltd.BT – Applied TechnologyBuro Happold, Ltd.China State Construction Engineering Corporation (CSCEC)Emaar Properties, PJSC Eton Properties (Dalian) Co., Ltd.HOK, Inc.Illinois Institute of TechnologyKohn Pedersen Fox Associates, PCKONE Industrial, Ltd.Lotte Engineering & Construction Co.Morin Khuur Tower LLCNBBJPermasteelisa GroupSamsung C&T Corporation Shanghai Tower Construction & Development Co., Ltd.Shree Ram Urban Infrastructure, Ltd.Skidmore, Owings & Merrill LLPTaipei Financial Center Corp. (TAIPEI 101)Turner Construction CompanyWoods Bagot

PATRONSArabtec Construction LLCBlume FoundationBMT Fluid Mechanics, Ltd.Durst OrganizationEast China Architectural Design & Research Institute Co., Ltd.FC Beekman Associates, LLCGenslerHongkong Land, Ltd.KLCC Property Holdings BerhadMeinhardt Group InternationalStudio Daniel LibeskindThornton Tomasetti, Inc.Tishman Speyer PropertiesWeidlinger Associates, Inc.Zuhair Fayez Partnership

DONORSAdrian Smith + Gordon Gill Architecture, LLPAmerican Institute of Steel ConstructionAon Fire Protection Engineering Corp.ARCADIS/The Rise Group LLCArupAureconBesix SABollinger + Grohmann IngenieureC.Y. Lee & Partners Architects/PlannersCCDI (China Construction Design International) Group Enclos Corp.Fender KatsalidisHalfen USAHeerim Architects & Planners Co., Ltd.Hyundai Steel CompanyJacobsLaing O’RourkeLangan Engineering & Environmental Services, Inc.Larsen & Toubro, Ltd.Leslie E. Robertson Associates, RLLPMagnusson Klemencic Associates, Inc.Mooyoung Architects & EngineersPei Cobb Freed & PartnersPickard Chilton Architects, Inc.PT. Gistama IntisemestaRafi k El-Khoury & PartnersRolf Jensen & Associates, Inc.Rowan Williams Davies & Irwin, Inc.RTKLSaudi Binladin Group / ABC DivisionSchindler Elevator CorporationSeverud Associates Consulting Engineers, PCShanghai Construction (Group) General Co. Ltd.Shanghai Institute of Architectural Design & Research Co., Ltd.Shanghai Jingang North Bund Realty Co., Ltd.SIAPLAN Architects and PlannersSolomon Cordwell BuenzSsangYong Engineering & Construction Co., Ltd.Studio Gang ArchitectsSWA GroupSyska Hennessy Group, Inc.Tongji Architectural Design (Group) Co., Ltd.ViraconWalter P. Moore and Associates, Inc.Werner Voss + PartnerYolles

CONTRIBUTORSAedas, Ltd.ALHOSN UniversityAlvine EngineeringAmerican Iron and Steel InstituteAyala Land, Inc.Barker Mohandas, LLCBates SmartBenoy LimitedBonacci GroupBoundary Layer Wind Tunnel LaboratoryBritish Land Company PLCBroadway Malyan Asia Pte LtdC S Structural Engineering, Inc.Canary Wharf Group, PLCCanderel Management, Inc.CBRE Group, Inc.CCL Qatar w.l.l.Continental Automated Buildings Association (CABA)Daelim Industrial Co., Ltd.Davis Langdon & Seah Singapore Pte. Ltd.DBI Design Pty LtdDCA Architects Pte LtdDeerns Consulting EngineersDHV Bouw en Industrie

DK Infrastructure Pvt. Ltd.DongYang Structural Engineers Co., Ltd.Dow Corning CorporationEllumus LLCEW Cox Hong KongFar East Aluminium Works Co., Ltd.Goettsch PartnersGraziani + Corazza Architects Inc.HAEAHN Architecture, Inc.Hiranandani GroupHyder Consulting (Shanghai)International Paint Ltd.JCE Structural Engineering Group, Inc.Jiang Architects & EngineersKHP Konig und Heunisch PlanungsgesellschaftLend LeaseLiberty Group PropertiesM Moser Associates Ltd.Mitsubishi Electric CorporationMori Building Co., Ltd.MulvannyG2 ArchitectureMutua MadrilenaNabih Youssef & AssociatesNational Fire Protection AssociationNational Institute of Standards and Technology (NIST)Nishkian Menninger Consulting and Structural EngineersNorman Disney & YoungOrnamental Metal Institute of New YorkOtis Elevator CompanyParis La DéfenseParsons Brinckerhoff PDW ArchitectsPerkins + WillPomeroy Studio Pte LtdPositivEnergy Practice, LLCRAW Design Inc.Rosenwasser/Grossman Consulting Engineers, PCSAMOO Architects & EngineersSanni, Ojo & PartnersSilvercup StudiosSilverEdge Systems Software, Inc.SIP Project Managers Pty LtdSteel Institute of New YorkTekla Corp.Terrell GroupThyssenKrupp Elevator TSNIIEP for Residential and Public BuildingsUniversity of Illinois at Urbana-Champaignwh-p GmbH Beratende IngenieureWilkinson Eyre ArchitectsWSP Group

PARTICIPANTSACSI (Ayling Consulting Services Inc)Aidea Philippines, Inc.AKF Group, LLCAl Ghurair Construction – Aluminum LLCAl Jazera ConsultantsALT Cladding, Inc.ARC Studio Architecture + UrbanismArcelorMittalArchitects 61 Pte., Ltd.Architectural Design & Research Institute of Tsinghua University Architectural Institute of KoreaArchitectusArquitectonica International Corp.ASL SencorpAtkinsBakkala Consulting Engineers LimitedBAUM Architects, Engineers & Consultants, Inc.BDSP PartnershipBeca GroupBFLSBG&E Pty., Ltd.BIAD (Beijing Institute of Architectural Design)Bigen Africa Services (Pty) Ltd.Billings Design Associates, Ltd.bKL Architecture LLCBluEntBoston Properties, Inc.Bouygues ConstructionCallison, LLCCamara Consultores Arquitectura e IngenieríaCapital GroupCase Foundation Co.CB EngineersCCHRB (Chicago Committee on High-Rise Buildings)CDC Curtain Wall Design & Consulting, Inc.China Academy of Building ResearchChinachem GroupCICO Consulting Architects and EngineersCity Developments LimitedCode Consultants, Inc.Cook+Fox ArchitectsCosentini AssociatesCOWI A/SCox Architecture Pty. Ltd.CPP, Inc.CS Associates, Inc.CTL GroupCundallDam & Partners ArchitectenDar Al-Handasah (Shair & Partners)Degraeuwe ConsultingDelft University of TechnologyDennis Lau & Ng Chun Man Architects & Engineers (HK), Ltd. dhk Architects Pty., Ltd.DSP Design Associates Pvt., Ltd.Dunbar & BoardmanEdgett Williams Consulting Group, Inc.EEI CorporationEight Partnership Ltd.Electra Construction LTDELU Konsult ABENAR, Envolventes ArquitectonicasEnnead Architects LLPEnvironmental Systems Design, Inc.Epstein

Fortune Shepler ConsultingFXFOWLE Architects, LLPGale International / New Songdo International City Development, LLCGCAQ Ingenieros Civiles S.A.C.Glass Wall Systems (India) Pvt. LtdGold Coast City CouncilGorproject (Urban Planning Institute of Residential and Public Buildings)Grace Construction ProductsGreyling Insurance BrokerageGrupo ElipseGuangzhou Scientifi c Computing Consultants Co., Ltd.GVK Elevator Consulting Services, Inc.Halvorson and PartnersHaynes-Whaley Associates, Inc.Heller Manus ArchitectsHilson Moran Partnership, Ltd.Hong Kong Housing AuthorityHong Kong Polytechnic UniversityHousing and Development BoardIECA Internacional S.A.Institute BelNIIS, RUEINTEMAC, SAIrwinconsult Pty., Ltd.Iv-Consult b.v.Jaros Baum & BollesJBA Consulting Engineers, Inc.JMB Realty CorporationJohn Portman & Associates, Inc.JV “Alexandrov-Passage” LLCKajima Overseas Asia Pte LtdKalpataru LimitedKEO International ConsultantsKinetica Dynamics Inc.King Saud University College of Architecture & PlanningKorea UniversityKorean Structural Engineers AssociationKPMB ArchitectsLCL Builds CorporationLeigh & Orange, Ltd.Lerch Bates, Inc.Lerch Bates, Ltd. EuropeLiving Architecture Inc.Lobby AgencyLouie International Structural EngineersMace GroupMagellan Development Group, LLCMargolin Bros. Engineering & Consulting, Ltd.McHugh Construction Co.McNamara / Salvia, Inc.Metropro Consultants India Pvt. Ltd.Murphy / Jahn Architects LLCNikken Sekkei, Ltd.NW Project Management LimitedO’Connor Sutton CroninOdell Associates, Inc.Option One International, WLLP&T GroupPalafox AssociatesParagon International Insurance Brokers Ltd.Pelli Clarke Pelli ArchitectsPerkins Eastman Architects, PCPLP ArchitecturePowe ArchitectsPPG Industries, Inc.Profi ca Project ManagementProject and Design Research Institute “Novosibirsky Promstroyproject”Rafael Viñoly Architects, PCRead Jones Christoff ersen Ltd.Rene Lagos EngineersRiggio / Boron, Ltd.RMIT UniversityRonald Lu & PartnersRoosevelt University - Marshall Bennett Institute of Real EstateSauerbruch Hutton Verwaltungsges mbHSchlaich Bergermann und partner Sematic SPAShimizu CorporationSiemens IndustrySKS AssociatesSmithGroupSouthern Land Development Co., Ltd.St. Francis Square Development Corp.Stanley D. Lindsey & Associates, Ltd.Stauch Vorster ArchitectsStephan Reinke Architects, Ltd.Studio Altieri S.p.A.Taisei CorporationTakenaka CorporationTameer Holding Investment LLCTandem Architects (2001) Co., Ltd.Taylor Thomson Whitting Pty., Ltd.TFP Farrells, Ltd.Thermafi ber, Inc.TranssolarTrump OrganizationTyrénsUnited Elevator Consultants, Inc.University of Maryland - Architecture LibraryUniversity of NottinghamUralNIIProject RAACSVanguard Realty Pvt., Ltd.VDA (Van Deusen & Associates)Vipac Engineers & Scientists, Ltd.VOA Associates, Inc.Walsh Construction CompanyWeiss Architects, LLCWerner Sobek Stuttgart GmbH & Co., KGWindtech Consultants Pty., Ltd.WOHA Architects Pte., Ltd.Wong & Ouyang (HK), Ltd.WordsearchWorld Academy of Science for Complex SafetyWSP Cantor SeinukWSP Flack + Kurtz, Inc.WTM Engineers International GmbHWZMH ArchitectsY. A. Yashar ArchitectsZiegler Cooper Architects

Inside | 3CTBUH Journal | 2012 Issue IV

“The challenges associated with the inherent inconsistency of air flow may open a new way of thinking about tall buildings as highly adaptive, dynamic systems capable of responding to the opportunities and challenges associated with spatially and temporally fluctuating resources.”

Menicovich et al., page 18.

News and Events

This Issue Dennis Poon CTBUH Trustee

CTBUH Latest Antony Wood CTBUH Executive Director

Debating Tall: Tall Buildings: A Sustainable Future for Cities?

Global News Highlights from the CTBUH global news archive

02

04

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06

Case Study

Absolute World Towers, Mississauga Bas Lagendijk, Anthony Pignetti & Sergio Vacilotto

12

Research

A Different Approach to the Aerodynamic Performance of Tall Buildings David Menicovich; Jason Vollen; Michael Amitay; Chris Letchford; Edward DeMauro; Ajith Rao & Anna Dyson

Increasing Problems of Falling Ice and Snow on Modern Tall Buildings Michael Carter & Roman Stangl

A Proposal to Create an Energy-Producing Megatall for Kunming, China Thomas Kraubitz

Assessing Potential Development in South Korea’s Supertall Building Technology Payam Bahrami, David Scott, Eun-Ho Oh & Young-Ho Lee

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36

Features

Tall Buildings in Numbers Canada Rising

Talking Tall: Bjarke Ingels has BIG Plans for Tall Buildings Bjark Ingels

Design Research CTBUH International Student Design Competition 2012

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46

CTBUH

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52

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Inside

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48 | CTBUH 9th World Congress Shanghai CTBUH 9th World Congress Shanghai | 49CTBUH Journal | 2012 Issue IV CTBUH Journal | 2012 Issue IV

When Shanghai Vice Mayor Shen Jun took the stage to offi cially open the CTBUH 9th World Congress, he quickly set the tone for the issues that would dominate the next three days of discussion and debate. “Land resources are not renewable,” Mr. Jun said. “We have no choice but to build high rises to save land effi ciently.” Tall buildings, he emphasized, must serve as solutions to China’s long-standing urban issues of pollution and over-crowding. “It is an urgent and critical task to meet these challenges.”

World Congress Draws Global Industry Leaders to Address Key Issues

(Left to right) Qing Wei Kong, Shanghai Tower; Timothy Johnson, CTBUH Chairman; Shen Jun, Shanghai Vice Mayor; Antony Wood, CTBUH Executive Director; Guo Qing Li, Tongji University. © CTBUH

Report by Kevin Brass, CTBUH Public Aff airs Manager

CTBUH Report: CTBUH 9th World Congress Shanghai

Working Groups Shanghai provided an opportunity for the CTBUH’s array of working groups to gather and plot strategy for new and on-going projects. The sessions which took place the day before the congress – included a roundtable meeting of CTBUH leaders, which attracted more than 30 active representatives from around the world. The rousing discourse primarily focused on the fl edgling city representative program and the best ways to grow the Council’s initiatives on a grass roots level.

Two of the working groups touted the release of new technical guides – Outrigger

The ballroom of the Grand Hyatt Jin Mao was packed to capacity for the opening ceremo-nies. The Congress sold out weeks before the opening, with 850 registered delegates from 43 countries in attendance, including many of the top developers, architects, engineers and building owners from China and around the world. “We purposely brought together a wide range of expertise and viewpoints, including the developers that are leading the tall building boom in Asia,” said CTBUH Executive Director Antony Wood.

The CTBUH 9th World Congress closed to rave reviews, after three days of in-depth presentations, lively panel discussions and networking events.

Asia was the centerpiece of the event, which was titled, “Asia Ascending: the Age of the Sustainable Skyscraper City,” but discussions inevitably focused on issues aff ecting cities and builders around the world. From the outset, CTBUH Chairman Timothy Johnson, a design partner at NBBJ, challenged the audience. “Let’s fi nd new ways to make buildings more sustainable,” he said. “Let’s be innovative. Let’s fi nd ways to change the way we think of tall buildings.”

Attendees openly exchanged ideas and their experiences, providing a unique opportunity to go behind the scenes at many of the world’s biggest and most innovative projects. “We hope by sharing our experience and insight into the building system we would make a contribution to sustainable supertall buildings in the world,” said Qing Wei Kong, Shanghai Tower Chairman, striking a chord that would resonate throughout the event.

Shanghai Tower’s aspirations go far beyond its height. The developers want to make it the “most sustainable building in the world,” with green areas and a design that makes it a comfortable and effi cient part of Shanghai’s changing landscape.

Sustainability and the need to create effi cient and well-organized projects that integrate and enhance the urban environment were

Richard Tomasetti of Thornton Tomasetti, Vincent Tseof Parsons Brinckerhoff ; Rafael Vinõly and Tony Long of CB Richard Ellis engaged in the panel discussion. © CTBUH

Traditional dragon dance troupe performance at the opening ceremony. © CTBUH

Design for High Rises Buildings released by the CTBUH Outrigger Working Group, and Natural Ventilation in High-Rise Offi ce Buildings, a product of the CTBUH Sustainability Working Group (see advertorial on page 51.) The other working groups – Building Information Modeling; Fire & Life Safety; Research, Academic & Postgraduate; Seismic Design and Wind Engineering – focused discussions on developing research projects and the best ways to share the latest information in their respective fi elds.

consistent themes. Speakers focused on the complexities of developing large projects, from energy costs and project management to the political infl uence on iconic projects.

“We need to work together to fi nd a balance between iconic design and sustainability,” said Mehdi Jalayerian, executive vice president of Environmental Systems Design, during a rousing panel discussion on the opportunities and barriers to sustainability. “They clash at some point.”

Delegates shared information and designs for the latest projects, as well as the challenges projects are facing around the world. Over and over again, speakers emphasized that tall buildings are still a young typology and the industry is still wrestling with the issues of creating effi cient projects that address the needs of fast-growing cities.

“This is a huge challenge for us. It is still not a mature business model in China,” said Zhaohui Jia, general manager of the Greenland Group, one of the largest developers of tall buildings in China. “We are still trying to explore this business model.”

Tall buildings still play a unique role in cities, a point brought home by the plenary session featuring the owners/developers behind the past, present and future world’s tallest building.

Attendees of the Global Leaders workshop. © CTBUHAttendees of the sold out Congress listen to the Day 2 plenary session presentations. © CTBUH

CTBUH 2012 Student Competition winner Alexis De Bosscher; Johannes de Jong, KONE; Chris Wilkinson, Wilkinson Eyre. © CTBUH

Timothy Johnson issues research seed funding check to winner Dr. Kristen Day, New York University with Li Hongyu from sponsor AECOM. © CTBUH

“Skyscrapers We purposely brought together a wide range of expertise and viewpoints, including the developers that are leading the tall building boom in Asia.”

24 | Climate and Environment Climate and Environment | 25CTBUH Journal | 2012 Issue IV CTBUH Journal | 2012 Issue IV

Background

Troublesome ice and snow formations on buildings are in no way a new phenomenon. Building designers and owners have long struggled with the various aspects of winter precipitation. This has led to the development of standards and codes to address such topics as wind loads and snow loads during building design. However, the aspect of falling, sliding or windblown ice and snow from a building is a topic that has not been widely acknowledged, and consequently has generated little in the way of standards, guidelines or prescriptive building code requirements to assist designers. In addressing concerns, designers have largely relied on past experience or trial and error methods for reducing potential risks. The learning process industry-wide has been slow or non-existent due to the reluctant nature of various parties to discuss errors or incidents, for fear of litigation. Open discussion of the issues will accelerate the learning process around the emerging problems created by advancing façade performance and tall building design.

Modern Towers, New Issues

The façades of some recently completed high performance buildings are actively promoting hazardous ice and snow formations under typical winter conditions, rather than unusual, severe or infrequent weather conditions. This realization is unnerving, as modern high performance buildings often show only modest or questionable reductions in energy usage, at times falling short of their prediction models. Furthermore, building codes and

Increasing Problems of Falling Ice and Snow on Modern Tall Buildings

Reported incidents of hazardous ice and snow falling from buildings are on the rise, specifically for recently completed tall buildings. High performance façades have improved internal thermal performance, but increased the conditions for forming ice on metal and glass skins. This paper sheds light on the issues, describing the factors that contribute to icing and hazardous ice and snow formation, and provides methods to address these issues within the design process.Michael Carter

Table 1. Building Envelope Requirements – ASHRAE Standard 90.1 2004 – 2010 Comparison (Table 5.5-4, Building Envelope Requirements for Climate Zone 4 - Non-Residential) © ASHRAE

Research: Climate and Environment

Roman Stangl

Authors

Michael Carter, Director/ConsultantRoman Stangl, Director/Project Manager

Northern Microclimate Inc. (NMI)33 Water Street N.P.O. Box 277 CambridgeOntario N1R 5T8Canada

t: +1 226 444 0188f: +1 226 444 0183e: roman.stangl@northernmicroclimate.com; mike.carter@northernmicroclimate.comwww.northernmicroclimate.com

Michael CarterMichael is a director and the lead technical consultant of Northern Microclimate Inc., an architectural consulting fi rm that focuses on the prediction, evaluation and mitigation of falling ice and snow. He has contributed to publications with the National Institute of Building Sciences, Construction Specifi cations Canada and the International Conference on Snow Engineering. Recognized as an expert in his fi eld, Michael works with architectural and engineering fi rms, focusing on his ability to visualize and interpret the characteristics of a building design within its local micro-climate.

Roman Stangl Roman is a director and the lead project manager of Northern Microclimate Inc. A CTBUH member with international experience, he has been actively managing and consulting within the design and construction fi eld since 2005. Roman has contributed to publications with the National Institute of Building Sciences, Construction Specifi cations Canada and the International Conference on Snow Engineering.

Figure 1. Example of snow and ice freezing on vision glass panel. © NMI

“High performance façades have improved internal thermal performance, but increased the conditions for forming ice on metal and glass skins…”

standards have shown a trend towards increasing the performance of roof, wall, and glass assemblies, as evidenced by comparing ASHRAE Standard 90.1 between the 2004 and 2010 versions (see Table 1). Further exacerbating the issue of ice and snow formations on façades is the addition of various exterior elements intended to control solar gain, which ultimately serve as cold collection surfaces. As a result, reports of falling ice and snow incidents from high performance buildings over the last ten years have shown an increase in the frequency and severity of hazardous ice and snow formation. Although formal records of falling ice and snow incident reports do not yet exist, this trend has been identifi ed through a record of media accounts and project experience. New reports in the last two years have detailed dozens of falling, sliding or windblown ice and snow incidents in North America alone, including such buildings as the Duke Energy Building in Charlotte and the New York Times Building in New York.

Many of the events investigated by the authors have not been found to be caused by a single infl uencing factor, but rather by a list of factors that tend to have a cumulative eff ect. True, there are situations where a single design feature, such as a window sill/mullion confi guration or a solar shade device, has had a signifi cant impact on the formation of hazardous ice and snow. However, over the course of numerous building investigations, which includes multiple cold room laboratory tests conducted in collaboration with the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL), this is found to be the exception rather than the rule when it comes

to newly completed high performance buildings.

In the simplest of explanations, the currently achieved reductions in heat loss from many buildings’ interiors are promoting an increase in potentially dangerous ice and snow formations. As insulation values, glass technology, and building systems progress in the future to conserve energy, the corresponding further reductions in heat loss through the façade will only increase the probability of hazardous ice and snow formation and release, creating signifi cant challenges for building designers, owners and operators, with further impacts to public safety. Consequently, investigation and research into the causes of these issues is needed and is ongoing. However, at this time empirical data and/or detailed case studies have not been developed due to the reluctance of building owners and designers to discuss their challenges openly.

The following case examples are based on interviews with building owners and

operators of recently completed buildings, combined with reviews of incident and cold room test reports. The cases reveal interesting data that initially seemed counter intuitive, but can be explained when the individual design details are investigated.

Case Example 1Building Type: Tall, High PerformanceLocation: Northeastern United States

In this example (see Figure 1), observations of ice sheets were reported to form in the center of vertical vision glass of a recently completed building, and would subsequently release and fall to the busy street below. This report was taken with some skepticism as heat loss characteristics of a traditional window and frame relationship call for the exterior skin temperature of the center of the window to be the warmest location, since it is the furthest from the infl uence of the frame that would typically have the advantage of insulation or a thermally broken profi le. However, in this particular case the large insulated glass panels off ered an improved thermal performance over traditional glass and there was no spandrel panel, only a minimalistic metal frame. Thus, the glass panels were the main resistive component of the assembly, promoting ice to form directly in the center (the coldest location) of vertical vision glass panels. The key point to this example is the fact that the profi le of the assembly is producing skin temperatures that align with exterior temperatures during more typical winter precipitation events, thereby promoting an increase in frequency and severity of icing over more traditional wall assemblies. To be clear, the relationship between glass and frame is not the sole

cause, but likely a tipping point for this particular example. Other infl uencing factors could include: the move to more effi cient with under fl oor displacement ventilation systems, the heat loss characteristics of the whole façade as a system, and external factors such as elevation, building geometry and orientation to prevailing weather. Overall, this example reveals that as improvements in building performance are made, and exterior skin temperatures are reduced or at a minimum modifi ed, there is opportunity for hazardous ice and snow formations to occur in diff erent manners and amounts.

Case Example 2Building Type: Tall, High PerformanceLocation: Midwest United States

The second example (see Figure 2) also deals with the relationship between glass and frame. However in this case the focus is on ice and snow formations that accumulate on window sills or mullion caps at the base of vision panels. In this example, signifi cant ice formations were consistently forming at the edge of mullion caps and falling. Historically, sills or mullion caps of a relatively small dimension were not prone to hazardous ice formations, as heat loss through the curtain wall system would create suffi cient melting to avoid signifi cant ice formations. However,

2004 2010 % Change

Opaque Elements Insulation Min. R-Value Insulation Min. R-Value

Roof (Insulation entirely above deck) R-15 R-20 33%

Wall above grade (mass) R-5.7 R-9.5 67%

Steel-framed walls R-13 R-13 +R-7.5 Cont. 58%

Fenestration Assembly Max. U Assembly Max. U

Vertical glazing 0%–40% of wall U-0.57 U-0.50 14%

30 | Energy Energy | 31CTBUH Journal | 2012 Issue IV CTBUH Journal | 2012 Issue IV

The Concept

Current energy provision systems in China are heavily based on exhaustible fuels such as coal, hydrocarbons, and uranium. To fulfi ll China’s commitment to reduce carbon dioxide emissions per unit of GDP by 40 to 50% by 2020, new systems to reduce the infl uence on the environment must be considered. Cities are turning to tall buildings to address the need for space in urban settings, where little new land is available, but skyscrapers are typically big energy consumers. They also tend to be ineffi cient, due to the space needed for vertical circulation. The higher the building, the more lifts and vertical infrastructure needed, limiting the amount of usable fl oor space.

The Krafthaus can simultaneously address China’s need for more space and clean energy (see Figure 1). The concept combines a 750-meter-tall solar updraft tower –some-times called a “solar chimney” or simply a “solar tower” – and a climate responsive tall building. At the heart of the Krafthaus is a solar thermal power plant utilizing a combination of a solar air collector and the central updraft tube to generate a solar induced convective fl ow, which drives pressure staged turbines to produce electricity.

This solar facility is linked with a multi-programmatic vertical tower reaching up 215 fl oors. The tower can off er gardens, shopping, leisure, entertainment, and cultural facilities, in addition to offi ces and apartments – a complete vertical city. The 70-meter-wide solar tube at the core of the Krafthaus allows

China’s fast-growing urban population and need for sustainable energy sources require alternative development ideas. The Krafthaus, which combines an energy-producing solar tower with an environmentally-responsive, 215-story building, is one idea under consideration to address the issues facing China’s cities. The building has installed power capacity about 30 MW of electricity. With only a portion used by the building, the bulk of the energy would be fed into the local grid. Thomas Kraubitz

Author

Thomas Kraubitz, Senior Consultant

Happold Ingenieurbüro GmbH (Buro Happold)Pfalzburger Str. 43-4410717 BerlinGermany

t: +49 30 860 906 3146f: +49 30 860 906 66e: thomas.kraubitz@burohappold.comwww.burohappold.com

Thomas KraubitzThomas has been working in the fi eld of sustainable planning and design for over ten years and has developed a holistic view of buildings and the urban context. He has worked in diff erent climatic zones in consulting, project management, urban planning, urban design and architecture for Stefan Behnisch, Ken Yeang, and Rem Koolhaas, amongst others. As a Fulbright Scholar he was a Teaching and Research Assistant at Harvard University from 2007–2009. Since 2012 he is also a studio critic at the Technical University Berlin.

Figure 1. The Krafthaus, Kunming. © Thomas Kraubitz

Research: Energy

A Proposal to Create an Energy-Producing Megatall for Kunming, China

lifts and infrastructure to be placed inside the concrete tube. On each fl oor there is a horizontal installment area for building services and technical equipment 150 meters long which allows an open space and a very fl exible fl oor plan.as well as easy access for maintenance or replacement without taking up valuable rentable space.

The Krafthaus form of generating energy is simple, reliable, accessible, and based on

renewable materials. The principle of the system was fi rst described by Isidoro Cabanyes in 1903 and was revisited in the late 1970s by Michael Simon and Joerg Schlaich. They successfully demonstrated the concept in 1982 in a small testing installation in Manzanares, Spain. Combining the system with a tall building is, however, a new approach.

In order to realize the potential of the Krafthaus linked with a tall building, it is essential to fi rst study a commercial solar updraft tower in operation to gain technical and fi nancial input for the project. The solar tower testing facility in Manzanares provided valuable information; however it was limited by its height of only 195 meters and maximum power output of 50 kW. The research operation was too small to collect data on commercial energy production. With a larger chimney height the pressure diff erences increase the stack eff ect and a higher power output is possible.

In 2010, a solar chimney plant started operation in Jinshawan, Wuhai City, Inner Mongolia, China. The 200-kilowatt power generating unit can supply 400,000 kWh of electricity per year, saving the equivalent of 100 tons of coal and 900 tons of water,

Kunming

Jinshawan, Wuhai

Figure 2. Kunming annual average global radiation overlay. © Schlaich Bergermann Solar

“A conventional solar updraft power station consumes several hundred hectares of land, if it is designed to generate as much electricity produced by modern power stations using conventional technology…”

compared with thermal power generation. The RMB 1.38 billion (US$208 million) project calls for a full facility covering 277 hectares to produce a comparable output of 27.5 MW by 2013. But only data from prolonged operation will allow for a judgement on the perfor-mance of the power plant and its potential as real estate property. So far only limited information on its existence and operation is available and still has to be verifi ed.

Finding the Ideal Location

A conventional solar updraft power station consumes several hundred hectares of land, if it is designed to generate as much electricity produced by modern power stations using conventional technology, such as fossil fuels or nuclear energy. Until recently, most discussions of Krafthaus have focused on hot areas where large amounts of very low-value land is available, such as deserts. But the limited number of consumers and high infrastructure and transport costs in those periods have made it economically impractical.

One of the most important aspects for planning and running a solar power plant is global radiation. At fi rst it may seem that areas

with a high air temperature are most suitable but radiation weakening components of the atmosphere - such as clouds, aerosols and water vapour need to be considered as well for the right location for a solar updraft tower. Only by evaluating Meteotest/Meteonorm satellite data, which includes the solar weakening components that reduce the W/m² heat gain on surface, an informed decision for the most eff ective location be made. Very important is also a high possible temperature diff erence between day and night to allow a steady operation of the updraft tower that can safe heat during the day in water packs and releases it at night.

In China, the Yunnan Province off ers many ele-ments necessary for the solar updraft tower with up to 220–240 W/m2 of Annual Average Global Radiation. The site of the chimney plant in Jinshawan, Wuhai City, has a value of just 180–220 W/m2 and a much smaller population (400,000 people), which means higher infrastructure costs due to the distance to consumers.

After overlaying solar radiation maps and the study of population maps (see Figure 2), the City of Kunming, Yunnan Province, was identifi ed as an ideal site for this concept and preliminary discussions have taken place on the concept with local planning authorities. Solar radiation already plays a large role in Kunming, with 60 to 70% of its warm water provided by solar-thermal energy. The population of Kunming prefecture stood at 6.4 million in 2010 and it is expected to grow to become the largest metropolis of the region. The strong economy of the Great Kunming Area (GKA) largely depends on tourism and agriculture, with limited space due to its hills and mountains. The city, often called “Spring City,” has also received attention for its proximity to the emerging business opportunities with Association of Southeast Asian Nations (ASEAN) members, especially Vietnam. The specifi c climatic conditions allow several harvests a year and its picturesque setting makes it a national and international tourist destination. At the same time the most suitable areas for development are the prime farmlands on the lakeshore – off ering valuable views for new housing

9th World Congress Shanghai ReportKevin Brass

CTBUH 2012 Awards OverviewKevin Brass

CTBUH on the RoadCTBUH events around the world

Diary Upcoming tall building events

Reviews Review of new books in the CTBUH Library

Comments Feedback on past journal issues

Meet the CTBUH Javier Quintana de Uña

CTBUH Organizational Structure & Member Listings

Debating Tall: Tall Buildings: A Sustainable Future for Cities | 5CTBUH Journal | 2012 Issue IV

YES Lester Partridge, Global Director, AECOM

The preservation of arable land and the regeneration of ecosystems must be first and foremost in any consideration for developing a sustainable community. Without the current finely balanced ecosystems our food production will be under threat and society as we know it cannot be sustained.

Tall buildings provide the opportunity for our expanding urban centers to increase population density with no reduction in arable land area. Tall buildings compress infrastructure requirements and provide opportunities for increased efficiencies. And although the buildings themselves may consume higher quantities of energy than low rise buildings, the opportunity for shared infrastructure such as district energy, waste to energy, water recycling and integrated public transport services provides significant efficiency benefits.

Debating Tall

Creating efficient, livable urban environments was a hot topic at the recent CTBUH World Congress. But are skyscrapers part of the equation? This month’s debate, “Are tall buildings an essential part of a sustainable urban future?”

predicament another diminishing return of having lived through an age of cheap energy and easy miracles: innovative things by nature have no track record of long-term success, and sometimes don’t work out, especially as basic economic conditions change. Innovation cannot be an end in itself.

It’s even likely that in the decades ahead work will no longer be organized in the way that made the skyscraper necessary – as it seemed, let’s say, back in the 1990s, when The Economist magazine cover story proclaimed that the world was “drowning in oil,” and Wall Street ramped up its operations for the final chapter of massive capital accumulation. As events ride the flux of evolution, we lose track of what reality may afford us, of what “normal” is – until one morning we get up and everything has changed.

NO James Howard Kunstler, author of “Too Much Magic: Wishful Thinking, Technology and the Fate of the Nation”

One big surprise awaiting us is the recognition that the skyscraper is obsolete. They have already exceeded their “sell-by” date categorically, but we have not received the message. Even the architecture establishment does not recognize the problem. It’s not primarily because of the issues of heating and air-conditioning, or about running all the elevators, though electric service may be a lot less reliable in the U.S. a decade from now. It’s because these buildings will never be renovated. They have one generation of life in them and then they are done. Buildings take a beating day after day and eventually all of them need to be thoroughly renovated. Note that the duration of time from completion of a building to first renovation has gone down significantly over the past hundred years due to added complexity and the use of “innovative” materials whose properties over time are unknown and untried.

Reduced energy supplies means proportionately reduced capital available for anything. We’ll be painfully short of financial resources and also of fabricated, modular materials – everything from steel to the silicon gaskets needed to seal glass curtain walls. The cities that are overburdened with skyscrapers will discover that they are liabilities, not assets. The skyscrapers deemed most “innovative” today – the ones most dependent on high-tech materials and complex internal systems – will be the most disappointing. This includes many so-called “green” buildings. Cities cannot be made of buildings that have no potential for adaptive re-use. We can easily see in this

In addition, the opportunity for local food production in tall building districts is enhanced through the integration of local market gardens. The proximity of these gardens can reduce the demand for transporting food. And where waste water can be collected from the precinct’s tall buildings, it can be recycled locally then re-distributed to where it is demanded in buildings and on local market gardens.

Tall districts also allow occupants to be within walking distance to services, work and recreation, thereby reducing the need for private transport usage. High speed transport links can connect a series of tall districts allowing occupants to easily commute to work. However, the critical benefit that a city of tall districts can provide is the opportunity to regenerate the local ecology between each area. Fingers of native fauna and flora can be reintroduced into our urban environments, putting a halt to the current rate of species depletion. And although we are yet to see this ideal model in practice, perhaps one of the best examples we have to date is Hong Kong, a city renowned for tall buildings. Hong Kong can boast that 40% of its land area is gazetted as natural habitats.

In summary, even though tall buildings on their own may not be an essential part of the sustainable future, they are an essential part of the future sustainable urban form. The challenge will be to convince city planners to place a moratorium on the development of all new green field sites and reacquire developed land within existing urban centers to promote native habitat. Indeed, not a popular decision for governments, as this will increase land values and the cost of home ownership, but a decision that will support the viability of tall building construction for the benefit of the planet.

Tall Buildings: A Sustainable Future for Cities?

6 | Global News CTBUH Journal | 2012 Issue IV

Visit the daily-updated online resource for all the latest news on tall buildings, urban development and sustainable construction from around the world at: http://news.ctbuh.org

Asia

The Hotel of Doom is back in the news. Photos of North Korea’s most famous unfinished building, the Ryugyong Hotel in Pyongyang, appeared on websites around the world after a tour group was given access to the interior of the 105-story, pyramid-shaped building, which was first started in 1992. The photos show a stark, unfinished shell behind the imposing glass façade. In November, the CEO of Kempinski Hotels said the hotel will “probably” open in 2013.

In Singapore, Tange Associates opened the 209-meter One Raffles Place Tower 2, which was designed by Paul Maritaka Tange. Tower 2 joins the 280-meter Tower 1, which was designed by his father, Kenzo Tange, and completed in 1986. “The opening of Tower 2 reflects the confidence property developers see in Singapore’s economy,” Deputy Prime Minister Tharman Shanmugaratnam said at the opening ceremony.

Developers are also showing confidence in Kuala Lumpur, where the Tradewinds Corporation is moving ahead with plans to demolish a pair of tower to make room for a new development to be called Tradewinds Towers. Demolition work is expected to commence in early 2013 on the RM6 billion

Ryugyong Hotel, Pyongyang. © Joseph Ferris III Abeno Harukas Tower, Osaka. © OgiyoshisanOne Raffles Place Tower 2, Singapore. © Tange Associates

Global News

(US$2 billion) project, which will include a 65-story office tower, a 54-story apartment tower, a 14-story medical center, a 24-story corporate office block and a retail plaza.

In Osaka, Japan, the Abeno Harukas Tower, owned by the railway company Kintetsu Corporation, topped out in August. The building, which will be Japan’s tallest upon completion, reached the landmark height of 300 meters when workers installed an 11-meter steel beam at the top of the structure. The building is scheduled for completion in 2014.

Also in Japan, Shimizu Corporation claims that its new Tokyo headquarters, which opened in August, is the world’s least Carbon Dioxide-emitting building. The company reportedly developed and adopted a variety of technologies in an effort to improve efficiency, cut gas and oil use, and reduce CO

2

emissions, including radiant heating and even solar installations. But there were skeptics; “There isn’t a clear certification standard for zero-energy buildings, which makes it difficult to verify this building’s claims,” Eric Bloom, a senior research analyst at Pike Research, told local media. “However, the building definitely uses a number of highly energy-efficient and CO

2-reducing features that aren’t commonly

seen in large buildings.”

Europe

After years of delays and false starts, St. Petersburg officials approved plans for natural gas company Gazprom’s Lakhta Center, a 463-meter building originally designed by RMJM on the city’s undeveloped outskirts. UNESCO blocked original efforts by threatening to strip the city of its World Heritage status if it allowed the skyscraper to be constructed too near the city center. USE builder Arabtec proudly trumpeted an AED453 million (US$123 million) contract to build the revised and relocated tower.

UNESCO was also making news in London, where the group warned officials to more closely regulate tall building development in the historic areas of the city. A UNESCO report called on the government to “regulate build-up of the area around the Shard” and asked to review major projects before an “irreversible commitment is made.”

Controversy flared up in August in Venice, where fashion mogul Pierre Cardin is planning to build a 244-meter Palace of Light in an underutilized area on the outskirts of the city. Citizens reacted strongly against the Palais de Lumiere’s avant-garde design. One Italian architect put it simply: “If you want to do something for Venice, do something else.”

12 | Absolute World Towers, Mississauga CTBUH Journal | 2012 Issue IV

Shapely Pair of Towers Challenges the Status Quo

Anthony Pignetti

Case Study: Absolute World Towers, Mississauga

Dubbed the “Marilyn Monroe” towers, the CTBUH 2012 “Best Tall Building Americas” award-winning project is the result of a unique public-private partnership and an international design competition, which chose a new Chinese firm doing its first work in North America. The innovative design, however, created an array of issues for the builders.

Like other suburbs in North America, the Toronto satellite community of Mississauga is quickly developing into an interdependent, urbanized area. Canada’s sixth largest and fastest-growing major city, Mississauga has a diverse economy and multicultural character, as well as a new-found status as an important city center in the Greater Toronto area (GTA). However, its rapid development into an urbanized center has been at the expense of a unique cityscape character.

The redevelopment of a major downtown intersection was seen as an opportunity to redefine Mississauga’s urban landscape through an innovative public-private partnership and internationally recognized architectural design. The project had to add something naturalistic and human to contrast with the existing backdrop of listless boxy buildings.

The winning design obeys many of the rules of the typical North-American high-rise: a central core, a straightforward and economic

Authors

Bas Lagendijk, Strategy Executive

MAD Architects 3rd Fl. West Tower 7 Banqiao Nanxiang, Beixinqiao Beijing 100007, China t: +86 10 6402 6632, f: +86 10 6402 3940 e: press@i-mad.com, www.i-mad.com

Anthony Pignetti, Vice President of Construction Sergio Vacilotto, Director of Site Operations

Dominus Construction Group 7777 Keele Street, Suite 216 Concord, Ontario L4K 1Y7, Canada t: +1 905 669 2200, f: +1 905 669 8867 info@dominus.ca, www.dominus.ca

Bas Lagendijk Bas Lagendijk deals with communication in Architecture at MAD. As a strategic thinker he informs on the potential of Architecture and communicates between clients, collaborators, governments, constructors and the general public.

Educated in Interior Architecture, Information Tech-nology and Graphic Design, he previously worked at OMA, where he was involved in many contemporary issues ranging from buildings to large scale sustain-ability issues such as Zeekracht, Roadmap 2050, West Kowloon Cultural District and the Venice Biennale.

Anthony Pignetti & Sergio Vacilotto Dominus Construction Group is a full service construction firm in the Greater Toronto Area. Draw-ing on the extensive industry expertise of senior management team members, Anthony Pignetti and Sergio Vacilotto, Dominus has distinguished itself within the industry as a new brand of builder focused on innovation and unique forms of partnership.

Dominus has earned a reputation for delivering projects unprecedented in engineering and technical complexity such as L-Tower, constructed atop of Toronto’s renowned Sony Centre for the Performing Arts, in addition to the Absolute World Towers – CTBUH 2012 Best Tall Building for the Americas.

Sergio Vacilotto

Bas Lagendijk structure and a glass façade. However, the outcome is fundamentally different in the perception of the people. By the time of completion the result was recognized by the public and news accounts as an inspiring place to live, something more than a place that strives for simple efficiency. The buildings hope to provide residents with an emotional connection to their hometown and neigh-bors, and a local landmark to define the city. A Risky Development Plan

The developers of the site, Fernbrook Homes and Cityzen Development Group, were determined to tackle the lack of a unique character when they set out to redevelop the intersection in Mississauga’s downtown core. It was determined that the best use for this important property would be a residential development. The entire project includes a master-planned community of five towers with more than 158,000 square meters, 1,850 residential units, a three-story 3,252-square meter recreation area, and retail facilities.

14 | Absolute World Towers, Mississauga CTBUH Journal | 2012 Issue IV

Figure 3. Typical floor plans of the Absolute World 56. © MAD

Figure 4. The towers‘ rotation difference. © PERI Figure 5. Typical structural configuration. © MAD

straightforward, with restrictions limited only to the amount and size of units. This allowed the competing designers full expression and flexibility.

Eschewing the tradition of accentuated verticality in high-rises, MAD’s design for the Absolute World Towers chose not to emphasize vertical lines. Instead, the design features smooth, unbroken balconies that wrap each floor of the building. In addition, at each successive level, the floor plate rotates in a range of one to eight degrees affording panoramas of the Mississauga skyline (see

Figure 3). By maximizing the viewing potentials both inside and outside the buildings, the design created a medium for social interaction throughout the balconies and connected the city dwellers with naturalistic design principles. Building an Idea

Many observers questioned whether the MAD design could actually be built. The unique features of this type of rotating structure had never before been subjected to Ontario building code requirements and there was no precedent for the construction challenges.

From the outset, local architectural and engineering firms were engaged to refine the design and ensure it would meet all local standards without compromising the initial design intent. While the lead time for most projects was normally three to four months before excavation was scheduled to commence, in the case of Absolute World, the preparatory period was extended to 12 months. This type of extensive pre-planning ensured the project was kept on schedule by anticipating potential issues.

While consultants always play a major role in the construction of any project, in this case their role was even more significant. The rotating design meant that every floor was unique. Meeting these challenges required extensive collaboration among all the

construction disciplines throughout the process.

In addition, there was some initial concern that the unique layouts would limit the ability to market and sell residential units in the tower. However, the interest generated by the competition and the public’s participation in the final selection helped the developers easily sell out the apartments in a few days. The developer had taken a significant gamble in committing to deliver a design developed out of a competition, but the results provided evidence that design does matter in the

Ground Level, -10° Level 40, 159°Level 24, 42°

18 | Wind Engineering CTBUH Journal | 2012 Issue IV

Introduction

While our environment consists mostly of fluids, we have primarily restricted ourselves to approaching investigations of the interactions between buildings and their surroundings by using solid modeling. As a result, the design of tall buildings has relied on both a Solid-based Aerodynamic Modification (SAM) approach to meet a desired aerodynamic performance and techniques to modify the geometry of the building (Geometry-based Aerodynamic Modification or GAM) or its structural properties, such as stiffness through the use of materials and auxiliary damping systems. Although these techniques do provide a narrow path for success, they do not adapt to fluctuating environmental conditions and are accompanied by a loss of useful floor area and an increase in total energy cost. SAM for Cross Wind Response Reduction

The development and increasing use of light-weight and high-strength materials in the construction of tall buildings, offering greater flexibility and reduced damping, has increased tall building susceptibility to dynamic wind load effects (Li et al. 2011) that limit the gains afforded by incorporating these new materials. The main associated risk is resonant oscillations induced by von-Kármán-like vortex shedding at or near the natural frequency of the structure caused by flow separation. The effects of dynamic wind loading increase proportionally with the

A Different Approach to the Aerodynamic Performance of Tall Buildings

This paper examines the use of Fluid-based Aerodynamic Modification (FAM) methods derived from flow control techniques first developed for the aerospace industry. Instead of relying on the adjustment of the solid material within the structure to improve the aerodynamics of a tall building, fluid-based active flow control is added to the building systems‘ matrix to manipulate the building boundary layer and achieve a desired performance for both the interior and exterior. Experimental results are presented to demonstrate proof of concept for the FAM approach to tall building aerodynamic modification.

Research: Wind Engineering

Authors

David Menicovich1 Jason Vollen,1Associate Director

Prof. Michael Amitay1

Prof. Chris Letchford1

Edward DeMauro2

Ajith Rao,3 Research and Policy Analyst Prof. Anna Dyson,1 Director

1Center for Architecture, Science and Ecology (CASE) Rensselaer Polytechnic Institute (RPI) 14 Wall Street, 24th Floor, New York, NY 1005 t: +1 212 618 3958, f: +1 212 667 0042 www.case.rpi.edu

2Rensselaer Polytechnic Institute 110 8th Street, Jonsson Engineering Center Rm. 2049 Troy, NY 12180 t: +1 518 276 6351, f: +1 518 276 6025 www.rpi.edu

3The Regulatory Assistance Project (RAP) 50 State Street, Suite 3, Montpelier, VT 05602 t: + 1 802 498 0703, f: +1 802 223 8172 www.raponline.org

David Menicovich is a Phd student at CASE, and is currently researching the development of building integrated flow control systems in collaboration with the Center for Flow, Physics and Control (CeFPaC) and the Department of Civil and Environmental Engineering (CEE) at RPI.

Jason Vollen is the Associate Director of CASE. He is a researcher focused on emerging material technologies, specifically, the integration of energy per-formative structural ceramics, dy-namic and environmental simulation, and digital fabrication.

Prof. Michael Amitay is a Professor and the James L. Decker ‘45 Endowed Chair in Aerospace Engineering at RPI, and the Director of the CeFPaC. Over the past few years Amitay has been exploring the feasibility of flow control to improve the performance of wind turbines in buildings.

Prof. Chris Letchford is the Head of Department of CEE at RPI. Dr. Letchford’s research work has largely focused on physical modeling of extreme winds and their impact on the built environment. Currently Dr. Lechford is involved in NYSDOT funded research on the aeroelastic response of slender structures and in the topographic effects of wind on wind turbine siting.

Edward DeMauro is a doctoral student at RPI whose research is focused on the study of active aerodynam-ic flow control through experimental methods.

Ajith Rao is a policy and research analyst at the RAP, where he works on providing technical and policy support to policymakers and regulators on a broad range of energy and environmental issues.

Prof. Anna Dyson is the founding Director of the CASE – a consortium which attempts to achieve a collaborative model without the schism that has typically divorced building science pursuits from the aesthetic, social and conceptual aspirations of architectural design inquiry.

power of the wind, causing tall buildings to pay a significant material price to increase the natural frequency and/or provide damping. In particular, crosswind response often governs both the strength and serviceability (human habitability) design criteria.

While both SAM and GAM strategies have merit, they often come at the expense of valuable leasable area and high construction costs, due to increased structural requirements for mass and stiffness, further contributing towards the high consumption of non-renewable resources by the building sector. Therefore, a traditional aerodynamic based solution comes at the cost of habitable, and therefore valuable, floor area that, in turn, may require additional compensatory stories, which further increase the wind loads and construction costs (Tse et al. 2009). A Novel Approach

While the SAM approach relies on the building, its geometry and material properties for aerodynamic performance, the proposed Fluid-based Aerodynamic Modification (FAM) approach is fundamentally different. Instead of adjusting the solid material to improve the aerodynamic shape of the structure, fluid-based flow control is used to manipulate the boundary layer characteristics (see Figure 1), i.e., the interaction domain between the building and the airflow, such that the airflow virtually “sees” a different shape. FAM is an Active Flow Control (AFC) strategy, i.e., a strategy that requires a power input and alters

Wind Engineering | 19CTBUH Journal | 2012 Issue IV

Figure 1. Schematic diagram showing a comparison of SAM that physically modifies the baseline building plan to reduce wind loads thus requiring additional compensatory stories, with FAM that controls airflow while preserving the baseline plan for economic optimization and maintenance of optimal Floor Area Ratio (FAR). © CASE

Figure 2. Schematic diagram of the research hypothesis: by affecting the crosswind force spectra on the building through the manipulation of the boundary layer, the required damping will be achieved through fluidic means, reducing the mechanical damping requirements of the building’s structure to achieve the desired serviceability criteria. © CASE

“Instead of adjusting the solid material to improve the aerodynamic shape of the structure, fluid-based flow control is used to manipulate the boundary layer characteristics, i.e., the interaction domain between the building and the airflow.”

the flow only when desired. The main goal is to mitigate flow separation in order to reduce the impact of shed vortices, reduce wind loading and decrease pressure fluctuations across the building envelope (see Figure 2). The FAM approach relies on concepts developed for Boundary Layer Control (BLC) and its application to date has been mainly in the aviation industry. While this has been powerfully demonstrated in airfoils – smooth shapes in uniform low turbulent flow and mean loads, it is the application to bluff bodies (buildings) in highly turbulent flow and the impact on fluctuating loads that remains to be clearly demonstrated.

The science of BLC originated with Prandtl (1904), who introduced boundary layer theory, explained the physics of flow separation and described several experiments where a boundary layer was controlled (Gad-El-Hak 2000). Since inception, two strategies for BLC have emerged;

1. Steady forcing: aerodynamic perfor-mance modification using steady flow. Boundary layer control, as a means of preventing separation, has traditionally been associated with the steady addition (blowing) of high momentum fluid, or the removal (suction) of decelerated fluid near a surface from a boundary layer to deflect the high-momentum free-stream fluid towards the surface.

2. Unsteady forcing: aerodynamic performance modification using periodic excitation. The second, more recent and more energy efficient approach, is periodic excitation, often regarded as oscillatory addition of momentum. As opposed to the steady flow strategy, which seeks to simply add or remove momentum to the flow, periodic excitation takes advantage of knowledge of naturally occurring frequencies within the flow, and structures associated with them. Therefore, periodic excitation may be used to alter more effectively the steady characteristics of the flow by targeting the structures. (Nagib et al. 2004, Greenblatt & Wygnanski 2000).

Additionally, with a sufficiently high actuation frequency, it may be possible to achieve virtual shaping of the object, where the flow effectively sees a different shape (see Figure 3). Although the unsteady forcing strategy is more complex than steady forcing, it has three main advantages: power requirement is an order of magnitude smaller, actuators can be decoupled from a main propulsive system, and they are autonomous, small and light-weight (Greenblatt & Wygnanski 2000). Synthetic jets (which neither add nor subtract mass from the flow field, i.e., zero-net mass flux) are used as periodic excitation actuators in the present work. These actuators operate by the periodic motion of a diaphragm that is (typically) driven by a piezoelectric disc (Glezer & Amitay 2002).

The addition of momentum by forcing is generally quantified using the blowing ratio, Cb:

Where Uj is the jet velocity and U∞ is the free-stream velocity and the momentum coefficient, Cµ:

Where ρj and ρ∞ are the densities of the jet and the free-stream velocity, respectively. Uj and U∞ are the jet and free-stream velocities. D, H, b, h are the model width, height, and jet orifice width and height, respectively.

Uj

U∞Cb = (1)

P – P∞ ρ∞U∞

2CP = 1

2

(3)

ρj Uj 2bh

ρ∞U∞2DH

Cµ = (2)

compensatory floor

separated flow

separated flow controlled

Uj

U∞Cb = (1)

P – P∞ ρ∞U∞

2CP = 1

2

(3)

ρj Uj 2bh

ρ∞U∞2DH

Cµ = (2)

Tall buildings: design, construction and operation | 2012 Issue IV

Inside Canada’s “Marilyn” Towers

Creating an Energy-Producing Skyscraper

Fluid-based Aerodynamic Performance

Ice, Snow and Tall Buildings

Assessing Korea’s Technology Potential

Talking Tall with Bjarke Ingels

In Numbers: Canada Rising

Reports: Shanghai Congress & 2012 Awards

CTBUH JournalInternational Journal on Tall Buildings and Urban Habitat

Council on Tall Buildings and Urban Habitat

S.R. Crown HallIllinois Institute of Technology 3360 South State StreetChicago, IL 60616

Phone: +1 (312) 567 3487Fax: +1 (312) 567 3820Email: info@ctbuh.orghttp://www.ctbuh.org

About the Council

ISSN: 1946 - 1186

The Council on Tall Buildings and Urban Habitat, based at the Illinois Institute of Technology in Chicago, is an international not-for-profi t organization supported by architecture, engineering, planning, development and construction professionals. Founded in 1969, the Council’s mission is to disseminate multi-disciplinary information on tall buildings and sustainable urban environments, to maximize the international interaction of professionals involved in creating the built environment, and to make the latest knowledge available to professionals in a useful form.

The CTBUH disseminates its fi ndings, and facilitates business exchange, through: the publication of books, monographs, proceedings and reports; the organization of world congresses, international, regional and specialty conferences and workshops; the maintaining of an extensive website and tall building databases of built, under construction and proposed buildings; the distribution of a monthly international tall building e-newsletter; the maintaining of an international resource center; the bestowing of annual awards for design and construction excellence and individual lifetime achievement; the management of special task forces/working groups; the hosting of technical forums; and the publication of the CTBUH Journal, a professional journal containing refereed papers written by researchers, scholars and practicing professionals.

The Council is the arbiter of the criteria upon which tall building height is measured, and thus the title of "The World’s Tallest Building" determined. CTBUH is the world’s leading body dedicated to the fi eld of tall buildings and urban habitat and the recognized international source for information in these fi elds.